create table t1(id not null) as select 1 from dual;
create table t2(id) as select 0 from dual;

create or replace view v1 as 
select t1.id i1, t2.id i2
  from t1
  left join t2 on t1.id = t2.id
 start with t1.id = 1
connect by prior t1.id + 1 = t1.id;

create or replace view v2 as 
select i1, t2.id i2
  from (select t1.id i1
          from t1
         start with t1.id = 1
        connect by prior t1.id + 1 = t1.id)
  left join t2 on i1 = t2.id;

SQL> desc v1
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 I1                                                 NUMBER
 I2                                                 NUMBER

SQL> desc v2
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 I1                                        NOT NULL NUMBER
 I2                                                 NUMBER